Motor vehicles are equipped with a windshield wiper device for wiping a surface of a windshield. The windshield wiper device may typically include a driving motor, a wiper arm and a wiper blade positioned on the surface of the windshield.
The driving motor functions to produce an oscillating movement. The wiper arm is coupled to a rotating shaft of the driving motor at its base end. The wiper blade is detachably joined to a distal end of the wiper arm. A component for biasing the distal end of the wiper arm toward the windshield is provided at the base end of the wiper arm. Thus, the wiper blade is placed in close contact with the windshield surface under the biasing force of the wiper arm and wipes the windshield surface while sliding thereon by oscillating movements produced by the driving motor.
The wiper blade typically has an elongated wiper strip and a frame component for attaching the wiper strip therealong and supporting the same thereon. The wiper strip may be made of a rubber-like material and be placed in contact with the windshield surface. The frame component may include an assembly having a plurality of yokes, or may include a single frame having a flat and elongated bar shape curved with a certain curvature. A wiper blade with a wiper frame of a yoke assembly is known in the art as “a yoke-type wiper blade,” whereas a wiper blade of a single flat bar-shaped frame is known in the art as “a flat wiper blade” or “a flat bar wiper blade.” One example of the yoke type wiper blade is illustrated in FIG. 1, while one example of the flat wiper blade is illustrated in FIG. 2.
Referring to FIG. 1, a yoke type wiper blade 10 includes: a wiper frame 12 having a main yoke 12a and a plurality of sub yokes 12b joined to the main yoke 12a in a bifurcated shape; and a wiper strip 11 attached to and supported by the sub yokes 12b. Referring to FIG. 2, a flat wiper blade 20 includes a flat bar frame 22 and a wiper strip 21 detachably fitted to an elongated slit defined in the flat bar frame 22 along a length direction thereof. The wiper blade 10, 20 is pivotally coupled to a distal end 31 of a wiper arm 30 at a middle section of the main yoke 12a or the frame 22.
The wiper strip 11, 21, which is equipped to the wiper blade 10, 20, has an inverted triangular cross-sectional shape at its edge. The wiper strip 11, 21 is placed in contact with a windshield surface along a tip edge 11a, 21a of such an inverted triangular cross-sectional shape. As the wiper blade 10, 20 is oscillated by the wiper arm 30 along with the operation of the drive motor of the windshield wiper device, the tip edge 11a, 21a of the wiper strip 11, 21 continues to wear out due to its slide contact to the windshield surface. Such wear might not occur constantly or uniformly along the tip edge 11a, 21a of the wiper strip 11, 21. Thus, after considerable wear, the tip edge 11a, 21a of the wiper strip 11, 21 is not placed in close contact with the windshield surface, but rather with any gap therebetween or any space coming off the windshield surface. Accordingly, when such a worn-out wiper strip is used, the windshield surface could not be wiped well and drivers could not clearly observe forward in a rainy or snowy weather. This may cause a traffic accident. To prevent such an event, the wiper strip (or the wiper blade with the wiper strip) needs to be replaced with a new one at an appropriate time.
As one example of prior art technologies addressing such a need, Korean Registered Utility Model Publication No. 20-0202621 suggests a wiper blade having a wiper strip with a replacement indicating protrusion adjacent to a tip edge of the wiper strip. This reference teaches users or drivers to make sure that the tip edge of the wiper strip has worn out up to the replacement indicating protrusion with his/her naked eyes.
However, it causes inconvenience to users or drivers to make sure how much the wiper strip has worn out with the naked eye. That is, users or drivers must swing up the wiper blade and then check the wear extent of the wiper strip. This causes considerable inconvenience to them. Further, when users or drivers forget to check the wear extent of the wiper strip, they cannot be aware that the wiper blade continues to wear out beyond a certain permissible limit and thus would miss an appropriate replacement timing of the wiper blade. As a result, they cannot help but to drive motor vehicles with considerably worn wiper blades not replaced.